This invention was made with Government support under Contract No. DE-AC05-96OR22464 awarded by the U.S. Department of Energy to Lockheed Martin Energy Research Corporation, and the Government has certain rights in the invention.
This invention relates generally to the preparation of structures utilizing a semiconductor-based substrate and relates, more particularly, to the formation of crystalline oxide thin films upon a substrate comprised of a Group IV material, such as germanium or silicon.
In U.S. Pat. No. 5,225,031, we described a process for depositing an oxide epitaxially onto a silicon substrate so that the structures which result from the process would be suitable for use in semiconductor and related applications. However, such a discussion was limited to the build-up of a crystalline oxide on silicon, a Group IV semiconductor material.
For use in some semiconductor devices, such as a transistor, having an epitaxial build-up of a crystalline oxide onto a semiconductor-based substrate, a germanium substrate is likely to provide better operating characteristics than those provided by a silicon substrate. For example, the electron hole mobility of germanium (related to the gain coefficient of the material) and which corresponds to the speed at which current can flow through the material is about four times higher in germanium than in silicon. Along the same lines, the switching speed (again, a function of electron hole mobility) is about four times faster in germanium than in silicon. Consequently, a transistor whose substrate is comprised of germanium could theoretically be switched about four times faster than a transistor having a silicon substrate. Therefore, it would be desirable to provide a generic process which can be used for constructing a crystalline oxide upon any Group IV semiconductor material, including germanium.
Accordingly, it is an object of the present invention to provide a process for growing a thin oxide film epitaxially upon a substrate comprised of elements from Group IV of the periodic table, and in particular, germanium or silicon.
Another object of the present invention is to provide a structure prepared by the process of the invention.
Yet another object of the present invention is to provide a structure which is well-suited for use in semiconductor and related applications.
A further object of the present invention is to provide a ferroelectric field effect transistor which embodies the structure of this invention.